1. Field of the Invention
This invention relates generally to material metering and, more particularly, to apparatus and method for conditioning semi-flowable material into an uncompacted state prior to volumetric metering to achieve a high degree of accuracy over a wide range of flow rates.
2. Description of the Prior Art
Fibrous material, such as strand fiberglass and asbestos, and certain powdery material, such as titanium dioxide, have a natural tendency to pack and bridge, thereby forming a substantially solid mass. Such material, hereinafter referred to as semi-flowable material, has always been difficult to handle in continuous and batch processes, due to the flow characteristics of such material. Semi-flowable material has a natural tendency to bridge at the hopper throat of typical prior art single stage feeding devices, resulting in inaccurate and inconstant flow rates. Illustrative of these prior art volumetric and weigh-type feeders are devices sold under the trademarks K-Tron.RTM., Vibrascrew.RTM., and Acrison.RTM..
Prior art feeders have, therefore, proved unsatisfactory in metering semi-flowable material. Typically, it is necessary to resort to weighing in order to achive accurate metering of such material.
It would be advantageous to provide a metering device for accurately metering semi-flowable material. Furthermore, it would be advantageous to provide such a device which is operable over a wide range of flow rates.